Injection apparatus with filter

ABSTRACT

A fluid medicament injection device is provided which has a housing, a chamber in the housing, a metallic filter dividing the chamber into forward and rearward portions, and a needle mounted for movement relative to the filter. In one position of the needle, it is in direct fluid communication with the forward portion of the chamber so that fluid flowing between the forward and rearward chamber portions is filtered by the filter, and in another position, the needle by-passes the forward chamber portion and the filter, and is in direct fluid communication with the rearward chamber portion.

United States Patent 1 Satchel! 1 1 June 5,1973

[ INJECTION APPARATUS WITH FILTER [75] Inventor: Fred E. Satchell, Chesterfield, Mo.

[73] Assignee: Sherwood Medical Industries Inc.,

St. Louis, Mo.

22 Filed: Feb. 15, 1972 211 Appl. No.: 226,615

[52] US. Cl ..128/2l8 R, 128/215, 128/234, 128/218 D [51] Int. Cl. ..A6lb 10/00, A61m 5/00 [58] Field ofSearch ..128/218 R,215,218 D, 128/224, 230, 234, 235

[56] References Cited UNITED STATES PATENTS 3,158,155 11/1964 Myerson et al ..l28/215 ,2,894,509 7/1959 Bednarz ....128/218 R 2,778,360 1/1957 Miskel ..128/218 D FOREIGN PATENTS OR APPLICATIONS 856,792 11/1952 Germany ..128/215 Primary ExaminerAldrich F. Medbery Att0rneyStan1ey N. Garber and William R.

OMeara [57] ABSTRACT A fluid medicament injection device is provided which has a housing, a chamber in the housing, a metallic filter dividing the chamber into forward and rearward portions, and a needle mounted for movement relative to the filter. In one position of the needle, it is in direct fluid communication with the forward portion of the chamber so that fluid flowing between the forward and rearward chamber portions is filtered by the filter, and in another position, the needle by-passes the forward chamber portion and the filter, and is in direct fluid communication with the rearward chamber portion.

20 Claims, 7 Drawing Figures INJECTION APPARATUS WITH FILTER BACKGROUND OF THE INVENTION This invention relates to medicament injection devices, and more particularly to a medicament injection syringe apparatus.

Conventionally, the distal end of a hypodermic needle of an injection device, such as a hypodermic syringe, is inserted through an enclosure member of an ampule containing medicament to draw medicament into the barrel portion of the syringe. Such enclosure members are often relatively thick rubber plug members. One serious problem in the use of conventional hypodermic syringes is that the needle as it passes through the rubber plug sometimes causes a coring thereof and there is the danger of particles of such coring entering into the medicament as it is drawn into the syringe. In addition to such particles, there is the danger that other debris or contaminations, such as crystallized medicament, may be passed into the syringe. Thus, the danger of injecting foreign particles or contaminations into the patient when using conventional hypodermic syringes under certain circumstances has been present.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a medicament injection device which substantially obviates the above mentioned disadvantages.

A specific object of the present invention is to provide a hypodermic injection device which substantially obviates the possibility of injecting contaminants into a patient.

Another object is to provide a novel hypodermic syringe having filter means for preventing the injection of undesirable particles into the patient.

Still another object is to provide a novel filter unit readily connectable between a syringe and a needle for filtering medicament.

In accordance with one form of the present invention, medicament syringe apparatus is provided which includes a housing having a chamber, a filter member in the chamber, and a cannula, the cannula and filter being relatively movable whereby the cannula, when in one position, has an opening in the chamber at one side of the filter member, and in another position, the opening in the cannula is on the other side of the filter member.

These, as well as other features and advantages of the present invention will become apparent from the following detailed description and accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FlG.'l is a longitudinal sectional view of a hypodermic syringe in accordance with one embodiment of present invention;

FIG. 2 is a sectional view of the hypodermic syringe of FIG. 1 showing the hypodermic needle in by-passing relation with the filter;

FIG. 3 is an enlarged cross-sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a longitudinal sectional view, with parts broken away, of a hypodermic syringe illustrating a modified embodiment according to the present invention;

FIG. 5 is a sectional view of the hypodermic syringe of FIG. 4, but with the needle in by-passing relation with the filter;

FIG. 6 is an enlarged cross-sectional view of the proximal end portion of the needle of FIG. 4; and

FIG. 7 illustrates medicament syringe apparatus in accordance with still another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, and particularly to FIGS. 1, 2 and 3, there is shown a medicament injection apparatus in the form of a hypodermic syringe 10 in accordance with a preferred embodiment of the invention. The hypodermic syringe 10 is shown including a syringe 12 having a transparent housing or barrel 14 and a plunger assembly 16 reciprocal in the barrel 14, a selectively movable needle and hub assembly 18, and a filter member 20 disposed in the barrel 14.

The plunger 16 includes a plunger rod 21 and a piston 22 connected to the forward or right-hand end thereof and which is in sealing, sliding engagement with the bore or chamber 23 of the barrel 14. The rod 21 is provided at the rearward or left-hand end with an enlarged plunger end 21a adapted to be engaged by the thumb. The piston 22 is preferably formed of rubber or the like. The barrel 14 is provided with a connector end portion 25 shown as an integral, longitudinally extending, distal end portion which is adapted to receive a hub 27 of the hub and needle assembly 18. A cannula, shown as a hypodermic needle 28, is fixed to the hub 27 in any suitable or conventional manner, and it extends through the hub and into an axially extending opening 29 in the forward end portion 25 of the barrel. Hub 27 is provided with an annular bead or rib 30 formed on the internal surface thereof which, in FIG. 1, is disposed between a pair of spaced external annular ribs 31 and 32 on the end portion 25 to predeterminately position the needle hub assembly 18 with respect to the barrel 14 and filter 20. The hub 27 is, of course, connected in sealing or fluid-tight engagement with the barrel. Another annular rib 33 is provided on end portion 25 for locating the assembly 18 in its second position, as will be explained hereinafter. Needle 28 is shown pointed at the opposite end portions 34 and 35, the ends being shown beveled. The needle 28 has a lumen extending between the opposite ends thereof with an inner opening 340 at the rearward or proximal end portion 34, and an outer opening 35a at the forward or distal end portion 35.

The filter member 20 is shown disposed in the barrel chamber 23 and divides the chamber 23 into rearward or proximal, and forward or distal, chamber portions, indicated respectfully at 23a and 23b. The filter member 20 includes a disc or annular plate element 40 formed of a filtering material and having a central aperture or opening 42 in aligned relation with needle 28 and which receives a seal or relatively thin plug member 44. Seal member 44 is formed of a suitable material such as rubber which will not break away or core when pierced by the needle 28. Seal member 44 is shown having a peripheral groove 46 which receives the inner wall of opening 42 in tight frictional engagement to secure the seal in the opening 42.

The material forming filter element 40, while it may be formed of any suitable material that will provide adequate filtering, is preferably formed of a metallic material, for example, a material formed of metal fibers bonded together, for example, by a sintering process, and then cut to the desired configuration. Depending upon the desired filtering characteristics, such materials as wire mesh, sintered powder, collimated metal type sheet, or the like, or non-metallic materials, can be used.

Filter member is secured in the forward end of the bore 23 with the outer periphery thereof in fluid tight engagement with the bore walls. In the illustrated embodiment, the outer periphery of the filter member 20 is circular and of a predetermined dimension relative to the bore 23 such that, when inserted from the open end of barrel 14 during assembly of the syringe, it is slidable into the bore 23 and has a tight friction fit therewith. The filter member bottoms against the radially inwardly inclined or conical forward portion of the barrel, indicated at 4'7, and which connects the main cylindrical barrel portion with the end portion 25. In this way, the filter member 26 remains in place adjacent the forward or right end of bore 23.

In operation, with the hub and needle assembly 18 positioned as shown in FIG. l and with the plunger assembly 16 in a forward position in the barrel, the distal end portion 35 of needle 2% is inserted, for example, into a vial of liquid medicament, and the piston 22 is retracted or moved rearwardly in bore 23 toward the left end thereof. Medicament is drawn up through the needle lumen into forward chamber portion 21%, through the filter element 40, and into the rearward chamber portion 23a, in response to the negative pressure in the barrel produced by the rearward movement of the plunger piston 22. In this way, the medicament is filtered by filter member 20 to provide a filtered medicament in the chamber portion 23a, which chamber portion serves as a reservoir chamber. Any foreign particles or other contamination will remain in the chamber portion 231; or be trapped by the filter member. Thus in FIG. l, the proximal end 34 of needle 28 is in the chamber portion 2% on the distal side of filter member 20, the needle lumen being in direct or unobstructed communication with the chamber portion 23b and opening 29 which is part of chamber portion 23b in the illustrated embodiment, so that the needle lumen is in series fluid communication with the chamber 23b, the filter member 2th,,and the reservoir chamber portion 230.

When it is desired to discharge the filtered medicament from the reservoir chamber 23a, for example, to inject such medicament into a patient, the hub and needle assembly I8 is first grasped and moved rearwardly relative to the syringe I2 to position the assembly 118 as indicated in FIG. 2. It is seen that the annular rib Bil) of the hub 27 is moved over annular rib 32 and 33 on the barrel extension 25. Thus, in FIG. 2, the needle and hub assembly is positioned with the needle piercing the seal member 44 of the filter member 20 and in fluidflow by-passing relation with the filter member so that the proximal end opening 341a of the needle lumen is disposed in the reservoir chamber portion 231; in direct fluid communication with the filtered medicament. When the outer distal end opening 35a of needle 28 is inserted, for example, in a patient, and a force applied to the rearward end of the plunger assembly 16, piston 22 moves forwardly in the barrel bore 23 forcing the filtered fluid medicament from the chamber portion 23a into the opening 340 of the needle, through the needle lumen, and out the end opening 35a and into the patient.

In the embodiment illustrated in FIGS. 1, 2 and 3, the barrel 14; and the hub 27 are shown formed of a plastic material and are of the disposable type. Also, the needle and hub assembly 18 is of the removable type which is readily slipped onto or removed from the forward end of the barrel.

Referring now to the embodiment illustrated in FIGS. 4, 5 and 6, a hypodermic syringe 50 is shown including a housing or barrel 51 having a metal connector extension 52 connected to the forward end thereof, a needle and hub assembly 54 coupled to the extension 52, and a filter member 56 disposed in the barrel 51. The needle and hub assembly 54 includes a hub 56 and a cannula or hypodermic needle 59 having a pointed distal end with an opening 60, and a proximal end 61 with an opening 62. Opening 62 is formed in the side wall of the needle. As seen more clearly in FIG. 6, the proximal end of the needle lumen, indicated at 64, is closed by a metal plug 63 which may, for example, be welded or soldered thereto. Hub 58 is provided with an internal annular bead or rib 65 disposed, in FIG. 4, between axially spaced external annular beads or ribs 66 and 67 on the syringe extension 52.

The filter member 56 is shown as an annular disc wedged or positioned in fluid-tight frictional engagement with the inner walls of the barrel bore, indicated at 69, to divide the barrel bore into proximal reservoir chamber portion 69a and a distal chamber portion 6%. In this case, the filter member 56 is provided with an opening 70 in aligned relation with needle 59 and which is only slightly larger or substantially the same size as the outer diameter of the needle. The needle 59 is slidable in the filter opening 70 and substantially closes the opening to substantially prevent fluid from flowing therethrough.

In FIG. 4 the hub and needle assembly 5d is positioned in a fluid filtering position with the end 61 of the needle 59 disposed in filter opening 70 to close the same and with the lumen opening 62 disposed within the forward chamber 691) and in direct fluid communication therewith. Thus, if the end opening 66 of needle 59 is disposed in a fluid medicament and the plunger, indicated at 72 in FIG. 4, is moved rearwardly in bore 69, the negative pressure produced thereby will draw fluid into the lumen of the needle 59, out the opening 62, into forward chamber portion 69b, through the filter member 56, and into the reservoir chamber portion 69a of the barrel 5E, The liquid medicament is thus filtered by filter 56.

When it is desired to dispense the filtered medicament in the chamber portion 69a, for example, to inject the same into a patient, the hub 58 is grasped and the assembly 54 is moved leftwardly relative to the barrel 51 to move the annular bead 65 over the rearward annular bead 67 on the syringe extension 52 to thereby position the hub and needle assembly 54 in a fluid discharge position with needle in fluid-flow by-passing relation with the filter member 56, as shown in FIG. 5. In this position, the proximal portion of needle 59 is moved rearwardly in the central opening 70 in the filter member 56 so that the proximal opening 62 of the needle is rearward of the filter member and disposed in direct communication with the reservoir chamber portion 69a. In this position, the filter opening 70 is also closed by the needle 59. After the needle 59 is inserted into the patient, the plunger is moved forwardly in barrel 51 to effect a positive pressure which acts on the filtered medicament in the chamber portion 69a to force fluid into the side-wall opening 62 in the needle 59, through the needle lumen, and out the distal end opening 60 and into the patient.

In the embodiment illustrated in FIG. 7, a syringe 80 is shown having a housing or barrel 81 and a piston assembly 82 with a piston 83 disposed within the barrel chamber or bore 84. The syringe has a lower conventional luer type end or tip 85 shown integrally connected therewith and which receives a filter unit, indicated generally at 87, which, in turn, has a needle and hub assembly 88 connected thereto.

The filter unit 87 includes a barrel or housing 90 having a chamber 91 dividing it into proximal and distal chamber portions 91a and 91b, respectively, by a filter member 95 disposed in fixed relation in the chamber 91. The housing 90 includes a proximal portion 90a having a luer opening 96 which slidingly and frictionably engages the luer tip or end 85 of the syringe barrel 81, and a distal portion 90b which receives the hub, indicated at 99, of the hub and needle assembly 88.

The hub and needle assembly 88 includes a hypodermic or hollow needle 100 having its proximal end opening indicated at 102 disposed in the distal chamber portion 91b, as shown in FIG. 7. Assembly 88 is similar to assemblies 18 and 54 of the embodiments illustrated in FIGS. 1 and 4 and includes an annular rib 103 on the inner surface of the hub 99.

The filter member 95 is shown identical to the filter member 20 in the illustrated embodiment of FIG. 1. Filter member 95 includes a filter element 104 and a central seal member 106 sealing a central opening therein. The seal member 106, which may be formed of rubber or the like, is adapted to be pierced by the proximal pointed end 102 of the needle 100 after medicament fluid has been drawn through filter unit 87 and into the barrel bore 84 of the syringe 80.

During the aspiration of fluid medicament into barrel bore 84, fluid flows into the distal end of needle 100, through the lumen of the needle, into chamber portion 91b, through filter element 104, chamber portion 91a, and into the bore 84 of the syringe 80. Such fluid flow is in response to negative pressures resulting from movement of the piston 83 leftwardly, as viewed in FIG. 7.

When it is desired to discharge the filtered medicament from the chamber 84, the hub and needle assembly 88 is moved rearwardly until the annular bead of rib 103 or hub 99 has moved, from the position shown in FIG. 7, over external annular beads, indicated at 108, on housing portion 90b of the filter unit 87. As the needle and hub assembly 88 is moved leftwardly, the inner end opening 102 at the proximal end of the needle pierces the seal 106 and is disposed in the proximal chamber portion 91a and in direct fluid communication with the filtered medicament in the barrel of the syringe 80. Upon movement of the piston 83 rightwardly, as viewed in FIG. 7, the fluid pressure acting on the medicament is forced into the opening 102 in the needle lumen so as to move fluid through the lumen and out the distal end of the needle. Since needle 100 is in by-passing relation with the filter member 95, the

flow of medicament from the barrel 84 to the distal end of the needle, of course, by-passes the filter member.

The filter unit 87 may be utilized with a conventional syringe barrel, such as of the type indicated at 81 in FIG. 7, and with a conventional needle and hub assembly of the piercing type, such as indicated at 88. Thus, the filter unit 87 can be stored separately and used when desired, and may be used with conventional syringes, and needle and hub assemblies.

In this illustrated embodiment, the housing of the filtering unit 87 is formed in two parts, a and 90b, which may be secured together such as by heat sealing or welding after the filter member has been disposed in the housing portion 90a. In the embodiment illustrated in FIG. 7, the syringe barrel 81, the housing 90 of the filter unit 87, and the hub 99 of the hub and needle assembly 88 are shown formed of plastic material, however, other materials, such as glass and metal, may of course be utilized where desired. Also, instead of utilizing the filter 95 and needle 100, a filter and needle similar to those shown in the embodiment illustrated in FIGS. 4, 5 and 6, may be used in the embodiment of FIG. 7 if desired.

In some cases, the fluid medicament injection apparatus illustrated herein may be operated by drawing unfiltered medicament into the reservoir chamber portion while the needle is positioned in series with proximal chamber portion but in by-passing relation with the filter member (as in FIGS. 2 and 5). Then, relative movement between the filter and needle is effected to locate the needle in a position in fluid flow series relation with the filter, and distal and proximal chamber portions (as in FIGS. 1, 4 and 7). In this case, the medicament flows through the filter and then through the needle in response to the positive pressure resulting from forward plunger movement so that filtering is accomplished during the discharge of medicament from the apparatus, for example, during the injection thereof into a patient.

While there is shown and described preferred forms of the invention herein, it will be understood by those skilled in the art the various changes and modifications thereto may be without departing from the true spirit of the invention, the scope of the invention being defined only by the appended claims.

I claim:

I. In fluid medicament injection apparatus, the combination comprising housing means having a chamber therein, filter means in said chamber for filtering fluid medicament flowing therethrough, said filter means dividing said chamber into a pair of chamber portions, and cannula means having spaced openings therein, said filter and cannula means being relatively movable to effect the positioning of one of said openings from within one of said chamber portions to a location within the other of said chamber portions.

2. The apparatus according to claim 1 wherein said filter means has an aperture therein for receiving said cannula means.

3. The apparatus according to claim 2 wherein said filter means includes puncturable seal means normally closing said aperture and which is punctured by said cannula in response to relative movement between said filter and cannula means.

4. The apparatus according to claim 2 wherein said cannula means is closed at one end and is sized to move in said aperture and substantially close said aperture.

5., The apparatus according to claim 4 wherein said one opening is disposed in the side wall of said cannula means.

6. The apparatus according to claim 2 wherein said housing means comprises a syringe barrel.

7. The apparatus according to claim 2 wherein said housing means comprises a member having one end with an opening adapted to receive one end of a syringe barrel, and an opposite end having an opening adapted to receive said cannula means.

8. The apparatus according to claim 1 wherein said filter means comprises a filter element of metal.

9. ln fluid medicament injection apparatus, the combination comprising housing means having a fluid chamber therein, filter means having an aperture therein and disposed in said chamber for filtering fluid flowing therethrough, said filter means dividing said chamber into distal and proximal chamber portions, cannula means, and coupling means connected to said cannula means and coupled to said housing means for movement relative thereto for selectively positioning said cannula means in a first position with said cannula means in direct fluid communication with said distal chamber and a second position with said cannula means in direct fluid communication with said proximal chamber portion and in fluid by-passing relation with said filter means and said distal chamber portion, said cannula means being movable in said aperture.

10. The apparatus according to claim 9 further including piston means slidable in said housing means for effecting fluid pressure in said chamber.

11. The apparatus according to claim 10 wherein said cannula comprises a hypodermic needle having distal and proximal openings respectively disposed in distal and proximal end portions thereof, said proximal end portion moves in said aperture during movement of said cannula from one of said first and second positions to the other of said first and second positions.

12. The apparatus according to claim 11 wherein said filter means includes seal means normally closing said aperture, and said proximal end portion has a pointed end for puncturing said seal means when said proximal end portion moves in said aperture.

13. The apparatus according to claim 11 wherein the proximal end of said proximal end portion is closed, said proximalopening is in the side wall of said proximal end portion, and said needle is sized to maintain said aperture substantially closed when said needle is in said first position and also when it is in said second position.

14. The apparatus according to claim 11 wherein said coupling means comprises a hub, said housing means comprises a main barrel portion, and a distal extension portion having a smaller outer diameter than that of said barrel portion for receiving said hub, and a generally radially inwardly extending portion connected between said extension portion and said barrel portion,

said hub and said extension portion having cooperating abuttment means thereon for selectively locating said hub relative to said housing means to position said cannula selectively in said first and second positions.

15. The apparatus according to claim 14 wherein said filter is disposed in said housing means in engagement with the juncture between said barrel and said extension portions.

16. A hypodermic syringe comprising a hub, a hypodermic needle fixed to said hub and having distal and proximal openings therein, a barrel having a bore, and a distal end portion receiving said hub to connect said needle in fluid communication with said bore, a filter disposed in said bore adjacent to said distal end portion and dividing said bore into distal and proximal chambers, said filter having a normally closed aperture therein aligned in relation with said needle, said hub and said needle being movable relative to said barrel to selectively position said proximal opening in said barrel on the distal side of said filter with said needle in series fluid communication with said distal and proximal chambers and said filter, and to position said proximal opening in said barrel on the proximal side of said filter with said needle extending in' said aperture in direct fluid communication with said proximal chamber and in fluid by-passing relation with said filter and said distal chamber, and plunger means including piston means slidable in said bore for moving fluid through said needle.

17. The hypodermic syringe according to claim 16 further including seal means normally closing said aperture, and wherein said needle pierces said seal means when moving from one of said sides of said filter to the other of said sides.

18. The hypodermic syringe according to claim 16 wherein said aperture is closed by said needle when said proximal opening is on said distal side of said filter and when it is on said proximal side of said filter.

19. The hypodermic syringe according to claim 16 wherein said filter comprises an annular disc-like member formed of metallic fibers.

20. A filter unit for use in filtering fluid medicament in medicament injection apparatus comprising a housing having a chamber, a filter having two faces and means for receiving a needle end, said filter being disposed in said chamber dividing said chamber into distal and proximal chamber portions respectively adjacent said faces, said housing having a proximal end portion for coupling a hypodermic syringe barrel thereto in fluid communication with the chamber, said housing having a distal end portion for sealingly receiving the hub of a needle and hub assembly for connecting the proximal opening end of the needle of said assembly selectively in said distal chamber and said proximal chamber. 

1. In fluid medicament injection apparatus, the combination comprising housing means having a chamber therein, filter means in said chamber for filtering fluid medicament flowing therethrough, said filter means dividing said chamber into a pair of chamber portions, and cannula means having spaced openings therein, said filter and cannula means being relatively movable to effect the positioning of one of said openings from within one of said chamber portions to a location within the other of said chamber portions.
 2. The apparatus according to claim 1 wherein said filter means has an aperture therein for receiving said cannula means.
 3. The apparatus according to claim 2 wherein said filter means includes puncturable seal means normally closing said aperture and which is punctured by said cannula in response to relative movement between said filter and cannula means.
 4. The apparatus according to claim 2 wherein said cannula means is closed at one end and is sized to move in said aperture and substantially close said aperture.
 5. The apparatus according to claim 4 wherein said one opening is disposed in the side wall of said cannula means.
 6. The apparatus according to claim 2 wherein said housing means comprises a syringe barrel.
 7. The apparatus according to claim 2 wherein said housing means comprises a member having one end with an opening adapted to receive one end of a syringe barrel, and an opposite end having an opening adapted to receive said cannula means.
 8. The apparatus according to claim 1 wherein said filter means comprises a filter element of metal.
 9. In fluid medicament injection apparatus, the combination comprising housing means having a fluid chamber therein, filter means having an aperture therein and disposed in said chamber for filtering fluid flowing therethrough, said filter means dividing said chamber into distal and proximal chamber portions, cannula means, and coupling means connected to said cannula means and coupled to said housing means for movement relative thereto for selectively positioning said cannula means in a first position with said cannula means in direct fluid communication with said distal chamber and a second position with said cannula means in direct fluid communication with said proximal chamber portion and in fluid by-passing relation with said filter means and said distal chamber portion, said cannula means being movable in said aperture.
 10. The apparatus according to claim 9 further including piston means slidable in said housing means for effecting fluid pressure in said chamber.
 11. The apparatus according to claim 10 wherein said cannula comprises a hypodermic needle having distal and proximal openings respectively disposed in distal and proximal end portions thereof, said proximal end portion moves in said aperture during movement of said cannula from one of said first and second positions to the other of said first and second positions.
 12. The apparatus according to claim 11 wherein said filter means includes seal means normally closing said aperture, and said proximal end portion has a pointed end for puncturing said seal means when said proximal end portion moves in said aperture.
 13. The apparatus according to claim 11 wherein the proximal end of said proximal end portion is closed, said proximal opening is in the side wall of said proximal end portion, and said needle is sized to maintain said aperture substantially closed when said needle is in said first position and also when it is in said second position.
 14. The apparatus according to claim 11 wherein said coupling means comprises a hub, said housing means comprises a main barrel portion, and a distal extensIon portion having a smaller outer diameter than that of said barrel portion for receiving said hub, and a generally radially inwardly extending portion connected between said extension portion and said barrel portion, said hub and said extension portion having cooperating abuttment means thereon for selectively locating said hub relative to said housing means to position said cannula selectively in said first and second positions.
 15. The apparatus according to claim 14 wherein said filter is disposed in said housing means in engagement with the juncture between said barrel and said extension portions.
 16. A hypodermic syringe comprising a hub, a hypodermic needle fixed to said hub and having distal and proximal openings therein, a barrel having a bore, and a distal end portion receiving said hub to connect said needle in fluid communication with said bore, a filter disposed in said bore adjacent to said distal end portion and dividing said bore into distal and proximal chambers, said filter having a normally closed aperture therein aligned in relation with said needle, said hub and said needle being movable relative to said barrel to selectively position said proximal opening in said barrel on the distal side of said filter with said needle in series fluid communication with said distal and proximal chambers and said filter, and to position said proximal opening in said barrel on the proximal side of said filter with said needle extending in said aperture in direct fluid communication with said proximal chamber and in fluid by-passing relation with said filter and said distal chamber, and plunger means including piston means slidable in said bore for moving fluid through said needle.
 17. The hypodermic syringe according to claim 16 further including seal means normally closing said aperture, and wherein said needle pierces said seal means when moving from one of said sides of said filter to the other of said sides.
 18. The hypodermic syringe according to claim 16 wherein said aperture is closed by said needle when said proximal opening is on said distal side of said filter and when it is on said proximal side of said filter.
 19. The hypodermic syringe according to claim 16 wherein said filter comprises an annular disc-like member formed of metallic fibers.
 20. A filter unit for use in filtering fluid medicament in medicament injection apparatus comprising a housing having a chamber, a filter having two faces and means for receiving a needle end, said filter being disposed in said chamber dividing said chamber into distal and proximal chamber portions respectively adjacent said faces, said housing having a proximal end portion for coupling a hypodermic syringe barrel thereto in fluid communication with the chamber, said housing having a distal end portion for sealingly receiving the hub of a needle and hub assembly for connecting the proximal opening end of the needle of said assembly selectively in said distal chamber and said proximal chamber. 